Tricuspid regurgitation (TR) adversely affects cardiac mortality in a number of clinical settings. In adults, “functional” TR from tricuspid annular dilation and right ventricular enlargement is a common TR mechanism and can be secondary to left-sided valve and ventricular dysfunction or pulmonary hypertension. Tricuspid annuloplasty (TAP) can be used to repair the tricuspid valve in cases of functional TR. Functional TR also occurs in children, but TAP is often not appropriate, because the treatment may impede the growth potential of the tricuspid annulus. The mechanism of regurgitation in functional TR and in children with some forms of congenital TR is thought to be tethering of the leaflets from outward displacement of papillary muscles in the dilated right ventricle, which often cannot be effectively treated by annuloplasty.